In a charged particle circulation apparatus (hereinafter also referred to as a storage ring) such as a synchrotron, perturbation is generated by using a perturbating device such as a perturbator, and thereby charged particles injected to the circulation apparatus are taken to a stable orbit (hereinafter also simply referred to as an orbit). After the particles are taken to the stable orbit, the charged particles circulating in the stable orbit may be accelerated using a high-frequency acceleration cavity.
As an example of a radiation light generator (X-ray generator) using an electron storage ring, MIRRORCLE radiation light generator has been known. MIRRORCLE radiation light generator is a small-size radiation light generator using weak-convergence synchrotron. In MIRRORCLE radiation light generator, electrons accelerated by a microtron are injected to a storage ring, and in order to put the injected electrons into the orbit, a perturbator is used. Specifically, a current of half sinusoidal wave (hereinafter also referred to as an excitation current) is caused to flow through a coil forming the perturbator, so that a pulse perturbation field is generated, and injected electrons are circulated. The excitation current of half sinusoidal wave is applied repeatedly with a prescribed period (for example, 1 ms (frequency: 1 kHz)), and every time the excitation current is applied, injected electrons are put into the orbit and the number of circulating electrons, or the storage current, increases. By way of example, the width of excitation current, which is a half sinusoidal wave, is about 150 ns and the timing window (width of beam current) at which the beam can be injected, is about 100 ns, as shown in FIG. 1.
Resonance injection has been known as a method of injecting an electron beam to the storage ring. Details of resonance injection method are disclosed in the following references and well-known. Therefore, detailed description will not be repeated here: T. TAKAYAMA, “Resonance Injection Method for the Compact Superconducting SR-Ring”, Nuclear Instruments and Methods in Physics Research, B24/25 (1987) 420-424 (Reference 1); H. YAMADA, “Commissioning of aurora: The smallest synchrotron light source”, J. Vac. Sci. Technol. B8 (6), November/December 1990, pp. 1628-1632 (Reference 2); and Takeshi TAKAYAMA, Takashi YANO, Yasushi SASAKI, Naoki YASUMITSU, “Injection System of Compact SR Light Source “AURORA””, Technical Report of SUMITOMO HEAVY INDUSTRIES, Vol. 39, No. 116, August 1991, pp. 11-18 (Reference 3).
In resonance injection method, a half sinusoidal wave is used as the perturbator excitation current, as described above, since it was believed that if the excitation current of continuous sinusoidal wave was caused to flow in the perturbator, stable circulation of electrons could not be achieved, since the negative portion of the excitation current (current in the opposite direction) affects the electrons that were once put into the orbit.
In the resonance injection method, injection of electron beams to the storage ring must be exactly timed with the introduction of excitation current to flow to the perturbator. This adjustment is very difficult, as it is influenced by the signal jitter (time jitter). In order to increase the amount of generated radiation rays (X-ray intensity), the number of electron injections should be increased. For this purpose, however, power source capacity must be increased, which is costly.
In order to solve these problems, the inventor of the present invention proposed a technique of injecting a charged particle beam to a storage ring while a current, of which intensity changes as a sinusoidal wave, is caused to flow continuously (WO2012/081070). According to this technique, a larger current can be stored in the storage ring than when a pulse perturbation magnetic field is generated by causing the excitation current of half sinusoidal wave to flow through the coil forming the perturbator.